APPLICANT'S ABSTRACT]: As increasing numbers of individuals enter treatment for alcohol dependence and abuse, an era of cost containment in health care challenges the cost effectiveness of traditional inpatient treatment. Clinical studies suggest that outpatient treatment for alcohol abuse and dependence may be as effective as inpatient treatment, and day hospital medical model programs have become a prominent outpatient modality. However, medical model programs are in general more expensive than non-clinical orientations such as the social model approach, although the effectiveness and cost of medical versus social model day treatment have not been assessed. Given the range and severity of problems commonly found among alcohol treatment clients, a question remains of what is the optimum approach for rehabilitation and whether this differs by gender, ethnicity, and psychiatric comorbidity. This study undertakes a controlled, random assignment comparison of two approaches to day treatment--the medical model and the social model--in "real world" agencies serving a heterogenous population (N=300; 28% women, 33% African American, and 33% Hispanic) reflective of many urban communities of individuals seeking help for their drinking. Using an intent to treat model, the study compares the effects of day medical model treatment and day social model treatment during the course of the care provided. It investigates differences in the approach taken to substance abuse treatment at the two programs, including the number and content of scheduled activities and services received, the role of staff, and areas stressed by the respective orientations. It compares post-treatment outcome and improvement rates in the areas of abstinence and alcohol consumption and drug use, levels of medical and psychiatric problems, levels of employment, legal and family/social problems, and supportiveness of social networks towards abstinence, and considers utilization of corresponding health and social services. The study aims to identify patient characteristics associated with successful treatment outcomes in each program orientation, and aspects of treatment associated with improvement at six and 12 months post-treatment. Finally, it compares the costs of day medical model and day social model treatment, and assesses relative cost and effectiveness of the two programs.